In contemporary communication systems it is known how to transmit user data, e.g. for voice or video communication, both by means of what is known as a circuit-switched technology and also via packet-oriented networks. Communication systems which support both a packet-oriented and a circuit-switching transmission technology are referred to in the following as >>convergent<< communication systems. As a result of the use of packet-oriented data transmission methods for communication systems of this type there are frequently losses in the quality of the user data to be transmitted, which losses are due primarily to an alternating conversion between a continuous user data stream and user data packets.
Taking the example of the commonly employed >>Internet Protocol<<, also referred to by the abbreviation IP, communication terminals which operate on the basis of a packet-oriented transmission technology will also be referred to in the following using the term >>IP communication unit<<. In the packet-oriented transmission of user data, for example voice data, the term >>Voice over IP<<, abbreviated to VoIP, is also current.
A convergent communication system typically comprises at least one communication device by means of which, through the use of suitable line/trunk modules, both IP communication terminals and >>classical<< communication terminals, i.e. communication terminals operating according to the circuit-switching principle, can be connected. In this case the communication devices are typically connected to one another and to further, what are referred to as >>remote<< units which for their part make a contribution toward switching and connection control.
In order to handle the conversion between circuit-oriented and packet-oriented transmission technologies, devices known as gateways can also be used in a convergent communication system. In this case a gateway performs a conversion between packet-oriented and circuit-oriented transmission technologies and is frequently disposed between a packet-oriented network and a communication device operating according to a circuit-switching method. Alternatively or in addition, subscriber modules and/or line/trunk modules of the communication devices as well as what are known as >>remote units<< are provided with functions of a gateway.
For remote units, communication devices and also for devices which take part as independent units in a call setup or switching operation in addition to the aforementioned units, the term >>node unit<< will also be used in the course of a more general description.
Furthermore, the term >>communication unit<< using in the following description includes terminals generally involved in a communication, such as e.g. VoIP communication terminals, analog as well as mobile or, as the case may be, cordless telephones, but also data terminals such as computer systems, mobile digital assistants, etc.
A convergent communication system is frequently characterized by a structuring into individual subnetworks, typically with each subnetwork being administered by a communication device or by a remote unit which, for the purpose of transmitting user or, as the case may be, signaling data, operate-according to a different transmission method depending on the respective necessary packet-oriented or circuit-oriented form of connection of the connected communication terminals.
In many cases a number of conversions, each time into the transmission method supported by the respective subnetwork, are necessary for a communication connection between two communication terminals that extends across several subnetworks using heterogeneous transmission methods. Said multiple conversions result in a loss in quality of the user data to be transmitted between the two communication terminals taking part in the connection.